Process of producing medullated artificial filaments



E. L. COE

April 6, 1948 PROCESS OF PRODUCING MEDULLATED ARTIFICIAL FILAMENTS Filed Sept. 26, 1944 INVENTOR.

Patented Apr. 6,1948

PROCESS OF PRODUCING MEDULLATED ARTIFICIAL FILAMENTS Elvin L. Coe, Nitro, W. Va., assignor to American Viscose Corporation, Wilmington,Del., a corporation of Delaware Application September 26, 1944, Serial No. 555,809

4 Claims. 1

This invention relates to methods of producin wool-like medullated artificial filaments and fibers. More specifically, the invention relates to methods of producing wool-like medullated artificial filaments and fibers from viscose.

Previously, in order to produce medullated artificial filaments or fibers from viscose, it .has been considered necessary to utilize viscose which had been ripened considerably beyond the age of viscose conventionally used for the manufacture of artificial filaments and fibers. The filaments and fibers obtained from such over-aged or over-ripened viscose were characterized by extremely low wet and dry tensile strengths. It was also suggested, in one instance, to produce such artificial filaments and fibers by spinning a viscose of extremely high viscosity, prepared by immediately xanthating unaged alkali cellulose, into a spinning bath containing abnormally high amounts of zinc sulfate.

When viscoseis extruded through a suitable spinneret or jet into a coagulating and regenerating bath, there is formed, first, a thin outer tube of regenerated cellulose, enclosing a core of fluid viscose, which fluid viscose is coagulated and regenerated subsequently by diffusion of the bath through the first-formed outer skin.

The present invention is based upon the discovery that it is possible to adjust the electrolytic concentrations of the fluid viscose core and the spinning bath, which affects the rate of diffusion of the bath through the outerskin, and thus makes it possible to control and retard the diffusion rate, so that the membraneous outer skin may be uniformly ruptured or cracked, by means of stretching, whilethe inner core of viscose which it encloses is still in the fluid state. According to my invention, such diffusion control is achieved by incorporating a soluble salt, notably sodium sulfate, with the viscoseat any point prior to extrusion of the latter into the spinning bath, and extruding the viscose into a spinning bath containing controlled amounts of sulfuric acid and zinc sulfate.

Generally speaking, thereis used in accordance with the present invention any normal viscose which is suitable for spinning artificial filaments accordin to the conventionalmethods, that is a viscose having a common salt'(sodium chloride) point of from about 2.7 to 4.1. However, it is preferred to use a viscose having a cellulose content in the neighborhood of about 8% and containing sodium hydroxide in relatively high concentration. The sodium hydroxide content of the. viscose however, is lower than 2 the cellulose content, for best results. The viscose may contain special modifying agents such as dulling agents, dyes, or pigments, or mixtures of such materials according to this invention;

The sodium sulfate may be added to the viscose in any amount, but it is preferred to use concentrations in the range of from about 2% to 10%, based upon the weight of the viscose, optimum results being usually obtained when the sodium sulfate is present in the viscose in a concentration of about 6 to 8%.

When proceeding accordin to this invention, viscose containing sodium sulfate is extruded into an aqueous coagulating and regenerating ,bath containing sodium sulfate and carefully controlled amounts of sulfuric acid, the latter being present in an amount of from 8 to 12%.

The bath may also contain up to 1.25% of zinc sulfate. I have found that, other conditions being as stated previously herein, the appearance of the filaments in cross-section can be predetermined, depending upon whether zinc sulfate is omitted from the spinning bath or present therein in controlled quantities. .Thus, ifzinc sulfate is omitted, or is present in an amount up to about 0.5%,,th filaments obtained have, in

cross-section, and along a predominant portion of the filament length, the shape of a horse-shoe the ends of which are comparatively widely spaced apart, whereas when zinc sulfate is present in the bath in amounts ranging from about 0.5 to about 1.25%, the filaments have, in crosssection, and along a predominant portion of the filament length, the configuration of a horseshoe the ends of which are substantially closed, or in some cases, even overlapped. I have found that whereas whenthe proportionate relationship of the bath constituentsis careful1y adjusted as indicated wool-like distinctly medullated filaments are obtained, if the bath contains sulfuric acid in an amount less than 8% or greater than 12%,and zinc sulfate in anamount in excess of 1.25%, medullated filaments cannot be obtained. The useful quantity of sodium sul- 3 from 8 to 12% sulfuric acid, about 1% zinc sulfate, and from 21 to 27% sodium sulfate.

The spinning bath is preferably maintained at a temperature of about 45 to 50 C.

After suitable immersion in the special coagulating and regenerating bath, the extruded filaments are withdrawnand subjected to stretching. The length of immersion of the filaments the bath, and the degree of stretch given them are important factors in achieving both rupturing or cracking of the outer membraneous tube of regenerated cellulose, and medullation. Slihe length of immersion of the filaments in the-ooag ulating and regenerating bath may be :varied somewhat but, in general, it is observed that best results are obtained with relatively short immersion distances, say in the neighborhood of about 14 to 80". may be used, depending upon the spinning speeds employed. The coagulation and regeneration is preferably efiected under-relaxed conditions, that is, the velocity-orthe filaments as they are drawn from the bathis maintained lower than the velocity of extrusion. .Afterwithdrawalfrom the bath, the filaments may be ,subjecte.d..-to stretching up to about50% of. their. length, but preferably ,a lower degree of stretchin can .the order of about ,15 to 2.0 is used.

This invention will be more readily understood by referenc to the.accomnonyingadrawing, in

' which Figure 4 is a diagrammatic viewrof-laspinning device which may be used ,for spinningwartificial wool-like filaments in accordance with :thepresentinventlon.

Referring to Figure .4, the'viscose containing from 2 to ,10 sodium sulfate is extruded through the orifices of spinneret 1 into an aqueous lcoagu- ,lating and regenerating. bath ,zhaving. the :composition set forth above and aintained :at about as to 50C.

The filaments are drawn .frQIn the-bath and passed over a soclet 3, and then overa second godet 4, thelatter rotating iat a peripheral-speed greater than the speed of godet 3, The filaments are stretched'between the godets. :Stretching may be effected by any customary or known means, and, if desired, godet A may lee-replaced byra tow-roll which receives filaments from a number-of spinnerets.

The filaments m-aythen be directed to a s table wind-up device, such as the centrifuge *5, shown in Figure 4, or, :it is desired to-ictltthem to-staple fiber length, they. *are directed: to; the :mouth of a cutting device; where they. are cutfin the wetstate, and then dried .During drying the :fibers tend :tos-piral and: that, together with th preferred relaxed. spinning ccnditions am pears to insure .a-permanent and natural crimp therein;

--.'I'hei-filaments.may zbez.-subiected. tothe usual after=treatments such asdesulphurizing,:etc, before. collection or cutting to. staple, lengths. Alternatively, .theymay be: artenprocessed uafter cpllectien or after cutting to staple fibers.

The artificial wool-like filaments andfibers produced accordin to this invention are medal,-

Of course, a wider rangeoflimits' lated, that is, they have, in cross-section, a horseshoe shape apparently caused by the filaments first forming a ribbon, and then folding in such a manner as to form a hollow tube with a slit on one side. The tube-like structure thus has a hollow, air-enclosing space or canal in the center thereof, providing occluded :air spaces, which impart to thefilaments or fibers insulating properties similar to those of natural wool. The products are characterized by a curled, kinky, or crimped form, which is assumed spontaneously snowmen :persists as one of their permanent structural characteristics. Because they are stretchedfiwhile the inner core of viscose is still inmelatiuely fiu-idvcondition the surface of the :filamentshasta series of substantially uniform transverse and longitudinal cracks, as shown at iiand 'L'i-n'Figure 1, which impart a roughness to the surface which is similar to, and has the same effect, particularly during textile processing, as the epidermal scales of natural wool fibers. The products of this invention arefur- 'ither characterized by a subdued lusteror .ma'ttlike appearance, which is natural, and'whichjis obtained without the addition to the viscose of any foreign deluster'ing agents, such aspigments, oils, or the like, although, of course, if desired, such foreign delustering a ents may be utilized. The fibers differ from standard rayon staple fiber in .theirfincreased power to absorhwater, and in their. different .dye index, the Ifibersobtained by the present jnventionhav'ing a .more pronounced ability to absorb dye. and being capable ,of being dyed ,darkerand deeper than standard staple .fibers, treated in the sameidye bath. Y

L'I'he productsof this invention are suitable. for a wide variety ofuses.

Because of theirmedullated :form, theypossess good insulating propertiesand, due .to their roughened or scaleelike surface and natural crimp, they show good .cohesiontor coherence in textile operations, where they may be processed,

either alone .or admixed in blendsfwith other fibers. r

The products may beutilized in. the form-of continuous filaments, or cut into staple of any desired length. Either .aloneerin admixture with Wool, crimped rayonstaple, standardstaple, .orithe like, they may be converted. into yarns by conventional procedures, asby spinningin accordance with the cotton, woolen, worsted, or modified systems. Fabrics composed of .such yarns possess unusual properties-as to fhand 0r.feel. v

The medullated artificial wool-like filaments produced according to my invention have been found to have tensile strengths ofuat least about 1 to 1%; ,gms./denier, and .extensibilitie's :of at least 10% to 25% when dry; .and to have tensile strengths of at .least about /2 to 1 vems/denier, and .extensibilities .ofat .least 10 to 40% when wet 'The following examples illustratemethods-of producing artificial .medullated wool-like filamentsand fibers accordingto my invention.

Example I .A viscose having=8% cellulose, 6.6% sodium hydroxide (based on the weight of the viscose), aged to a salt point of 3.5, andthaving a. ball fall viscosity of 65sec. and to which was added 8'% of sodium sulfate (based on the tweightvof .the viscose), Was extruded to form-filaments .or 'rs denier through a'spinneret having holes 2.5 mils 55 in diameter, into an aqueous coagulating and regenerating bath containing.

. Per cent Sulfuric acid i 10.5 Sodium sulfate 21 Zinc sulfate 1 at a temperature of 45 C. The filaments were immersed in the bath fora distance of 30 inches, and then gathered around a driven glass wheel. From the glass wheel, the" filaments-were passed to a tow-roll driven at a linear speedof 52 meters a minute, and given a stretch between the Wheel and tow-roll. The medullated filaments upon leaving the tow roll were directed to a cutting device and, after cutting, the fibers were opened and then dried. The fibers developed a permanent natural crimp during the drying procedure and were medullated.

Example II A viscose having 8% cellulose, 6% sodium hydroxide (based on the weight of the viscose) which was aged to a salt point of 3.6, and to which had been added 7.3% sodium sulfate (based Example III A viscose having 8% cellulose, 6.4% sodium hydroxide (based on the weight of the viscose), which was aged to a salt point of 3.6, and to which had been added 6.7% of sodium sulfate (based on the weight of the viscose) was extruded to form filaments of 5.5 denier through a spinneret having holes 2.5 mils in diameter, into a coagulating and regenerating bath as described in Example I. The filaments were immersed in the bath for a distance of 14 inches, and then handled as described in Example I. The products were medullated.

Example IV A viscose having 8% cellulose, 7% sodium hydroxide (based on the weight of the viscose) which was aged to a salt point of 3.2, and to which had been added 6.5% of sodium sulfate (based on the Weight of the viscose) was extruded to filaments of 5.5 denier through a spinneret having holes 2.5 mils in diameter, into an aqueous coagulating and regenerating bath containing Per cent Sulfuric acid 8.5 Sodium sulfate 21 Zinc sulfate 1 at a temperature of 50 C. The filaments were immersed in the bath for a distance of 19 inches, and then handled as described in Example I. The fibers thus obtained were medullated.

Example V A viscose having 8% cellulose, 6.6% sodium hydroxide (based on the weight of the viscose) which was aged to a salt point of 4.0 and to which had been added 6.0% of sodium sulfate minute.

(based on the weight'of the viscose) was extruded to filaments of 5.5 denier through a spinneret having holes 2.5 mils in diameter, into an aqueous coagulating and regenerating bath containing a Per cent Sodium sulfa 27 Sulfuric acid 11.5 Zinc sulfate 1 at atemperature of C. The filaments were immersed in the bath for a distance of 14 inches,

and then handled as described in Example I.

The products thus obtained were medullated.

Example VI 1 A viscose having 15%/cellulose, 6% sodium hydroxide (based on the weight of the viscose) which was aged to a salt point of 3.6, and to which had been added 7% of sodium sulfate (based on the weight of the viscose) was extruded to filaments of 5.5 denier through a spinneret having holes 2.5 mils. in diameter, into an aqueous coagulating and regenerating bath contain- 7 Per cent Sulfuric acid 9.5 Sodium sulfa 27.0 Zinc sulfate 1.25

at a temperature of C. The filaments were immersed in the bath for a distance of 14 inches, and then gathered around a driven glass wheel. From the glass wheel, the filaments were passed to a tow-roll driven at linear speed of 52.0 M./ Between the wheel and tow-roll, the filaments were treated with hot water (90 C.) and given a stretch of 15%. The medullated filaments upon leaving the tow-roll were directed to a cutting device, and handled as described in Example I.

7 Example VII A viscose having 8% cellulose, 6.6% sodium hydroxide (based on the weight of the viscose) which was aged to a common salt (NaCl) point of 2.7, and to which had been added 5% of sodium sulfate (based on the weight of the viscose), was extruded into an aqueuos coagulating and regenerating bath containing Percent Sulfuric acid 8 Sodium sulfate 21 Zinc sulfate 0.5

at a temperature of 45 C. The distinctly medullated filaments were handled in the manner described above. The filaments so obtained had,

in cross-section, and along a preponderant portion of their length, a substantially open horseshoe shape, as shown in Figure 3.

Since it will be apparent that the methods speci fically illustrated in the foregoing examples are capable of some modification without departing from the spirit of this invention, it is to be understood that the invention is not to be limited except as set forth in the appended claims.

This application is a continuation-in-part of my prior application, Serial No. 512,890, filed December 4, .1943, now abandoned.

In the claims, where the term fibers is used,

it is intended to define both continuous filaments and discontinuous fibers.

I claim:

1. A process for the production of artificial fibers having, in cross section, a horseshoe shape comprising the steps of spinning a normal viscose of normal spinning viscosity-i ha g; a salt point oi {rem 2.7 to 4 .1- and containing sodium sulphate into a coagulating and re enerating bath consistof an aqueous: solution of sulphuric acid in a concentration of from 8 to 12%, 21 to 27% sodiumsulphate, and from 0 to not more than 1.25%. of zinc, sulphate.

2. A process. for the produotionof artificial fibers having; in cross section, a horseshoe shape comprising the steps of spinning a. normal viscose of normal spinning viscosity having a salt point of from 237' to 4.1 and containing between Zand 10% of sodium sulphate based on the weight of the viscose, into a coagulating and regenerating bath consisting of an. aqueous solution of sulphuric acid in a concentration of from 8 to 12%, 21 to 27%sodium sulphate, and. from O to not more than 125%01 zinc. sulphate.v

3. A process for the production or artificial fibers having in, cross section, a, horseshoe shape comprising the steps of spinning a normal viscose of normal spinning viscosityhaving a salt point of from 227' to 41 and containing between 2 and 10% of sodium sulphate based on the Weight of the viscose into a coagulating and regenerating 25 bath consisting of an'aqueous solution of sulphuric acid in a concentration of from 8 to 121%, 21 to 27% sodium sulphate and from 0. to not more than 0.5% of zinc sulphate.

41A process star the production of artificial fibers having, in cross section,vv a. horseshoe shape comprising the steps of spinning a normal viscose of normal spinning viscosity havinga salt point r meanness elem The following references :are of recordiin the file of this patent:

UNITED STATES; PATENTS Number Name Date 1,683,199 Lilienield Sept. 4, 1928 2,302,077 K'ohorn Nov. 17, 1942 'FQREIGN: PATENTS Number Country Date 298,548 Great-Britain 0ct. 8, 1928 339,050 Germany July 12, 1921 342,641 Germany Oct; .2-1', 1921 

